1. Field of the Invention
The present invention relates to a printing apparatus, and more particularly a printing apparatus constituted by connecting an optional sheet feed unit (for example, a paper deck option unit) and a sheet ejecting unit (for example, sorter unit) to a main body of the printing apparatus and a device for controlling such connected optional equipment.
Also the present invention relates to a printing apparatus capable of printing by receiving text data from an external equipment such as a host computer, and more particularly to a printing apparatus capable of optimum selection of the sheet feed unit and the sheet discharge unit, and a control device for controlling the connected optional equipment.
2. Related Background Art
The conventional printing apparatus, such as a laser beam printer employing an electrophotographic process is constructed as shown in FIG. 27, in which a main body 201 of the image recording apparatus is provided with a video controller 202 and an engine controller 203 to be explained in the following.
The video controller 202 principally effects control relating to the image processing, and develops the image information, sent from an external apparatus (not shown) such as a personal computer through a general-use interface such as Centronics interface, into bit data. The engine controller 203 principally effects control on charging, exposure, development, image transfer, image fixing and sheet transfer relating to the electrophotographic process. A video interface 204 connects the video controller 202 and the engine controller 203, for enabling mutual communication.
A paper deck optional unit 205 stores a large amount of recording sheets, and supplies the printing apparatus 201 with the recording sheets, in response to an instruction from the engine controller 203. A paper deck interface 206 connects the engine controller 203 and the paper deck optional unit 205, for enabling mutual communication.
A sorter optional unit 207 is provided with plural stacker trays, and sorts the recorded sheets, coming out of the printing apparatus 201 into these trays according to an instruction from the engine controller 203. A sorter interface 208 connects the engine controller 203 and the sorter optional unit for enabling mutual communication.
In the above-explained configuration, upon receiving the image information and the print command from the external apparatus, the video controller 202 sends, through the video interface 204, a video signal, converted into bit data from the image information, and the print command to the engine controller 203. The video controller 202 also sends instructions on the use of the paper deck optional unit 205 and the sorter optional unit 207, based on an instruction of the user, entered from an operation panel (not shown) connected to the external apparatus or the video controller 202.
Then the engine controller 203 effects image recording based on the received video signal, by controlling components relating to the charging, exposure, image development, image transfer, image fixing and sheet transfer in the electrophotographic process, incorporated in the printing apparatus 201. Also at the same time, in response to an instruction from the video controller 202, it gives instructions on the sheet feed timing, etc. by controlling the paper deck optional unit 206 through the paper deck interface 206, and on the sheet sorting by controlling the sorter optional unit through the sorter interface 208.
However, such conventional configuration has been associated with the following drawbacks.
In the conventional configuration mentioned above, the engine controller and each optional unit are connected to one-to-one fixed relationship. For this reason, in order to increase the functions of the optional unit, it is necessary to improve the ability of the engine controller.
In recent years, the situation in which the electronic recording apparatus is used has become diversified, and it is therefore desired to expand the functions of the optional units and to freely combine various optional units. However, for enabling control on various optional units in the conventional configuration, the engine controller becomes costly as it has to control various objects in addition to the control on the electrophotographic process, and such additional cost is completely unnecessary for the user who does not use the optional units.
Also there has not been appropriate management among the data transferred from the host computer, the sheet feeding means and the sheet ejecting means for the sheets used for printing such data. For this reason, in case of recovery printing of several previous pages for the purpose of jam recovery, the sheet feed means and the sheet ejecting means are not necessarily same as those used prior to the occurrence of jamming, and the recovery print data have to be resent from the host computer in case special sheets such as colored sheets are employed or in case the sheet ejecting address is specified.
Also in case the sheet feed or ejecting unit is added as an option, the engine controller is required to have a high-performance CPU in order to effect control including such optional unit.
Furthermore, the information on such sheet feed or ejecting unit, such as the information on the time required for sheet feeding or ejecting in such unit, is not managed, and the selection of the sheet feed or ejecting unit is made by a default setting or a setting from the external apparatus. For this reason it has not been possible to achieve the printing operation within the shortest printing time.